3-D segmented ion trap
2015: Generation of squeezed "Schrödinger's cat" states
We follow the robust preparation of squeezed states with coherent quantum operations which create superpositions of an atom at two different positions. This type of superposition is commonly referred to as Schrodinger's cat states. Our "cats" are the largest achieved to date, when measured as the separation of the different positions divided by the ground state wavefunction (ratio = 20). When the wavepackets are squeezed, the separation divided by wavepacket size is three times larger (ratio = 60). These states may be of use for interferometry of quantum computing with continuous variables.
Work published in Nature: Hsiang-Yu Lo et al. Nature 521, 336–339 (2015).
News and Views article: T. Northup, Nature News and Views 521, 295-296 (2015)
Popular press coverage in ETH News, NZZ, and Spektrum der Wissenschaft.
2014: Harmonic Oscillator State Synthesis by Reservoir Engineering
We have synthesized quantum states of a harmonic oscillator using reservoir engineering. This allowed us to create a range of superposition states of the coherent motion of a trapped ion as the steady state of a dissipative process. We also introduced a novel method for characterizing oscillator states, which provides a clear measurement of the state fidelity by choosing the correct measurement basis.
Work published in Science: Daniel Kienzler et al. Science 347, 6217 (2015)
First beryllium + calcium ion chains loaded into the trap. We can simultaneously image both species through the same objective lens. The photo below shows a three ion chain, with a beryllium ion centred between two calcium ions. In the upper image, only the beryllium ion is shown, fluorescing at 313 nm. In the lower image the fluorescence at 397 nm from the calcium ions is shown.
Up to 2 Watts of Continuous-Wave light at 313 nm generated. High power 313 nm light is important for realizing quantum gates on beryllium ions with low error rates. These powers are more than sufficient for performing quantum gates at accuracies high enough for fault-tolerant quantum computation. Whether we are able to do this is another question! The light is generated by sum-frequency-generation of 626 nm light using 1550 nm and 1050 nm fibre lasers, followed by frequency doubling in a resonant cavity (shown below).
First calcium ions loaded into the trap. A photo of two ions is shown below.
This experiment aims to perform precision control of beryllium and calcium ions for quantum information processing, quantum simulation and quantum state engineering. The trap is fabricated from gold-coated laser machined alumina wafers, and is placed in a room-temperature ultra-high vacuum system. The smallest electrode you see is around 100 micron in width. Two in-vacuum objective lenses with a numerical aperture of 0.45 are used to image the ions. A picture of the trap is shown below.